1. Field of the Invention
The present invention relates to an organic electroluminescent (EL) display.
2. Description of the Related Art
Organic EL displays are of a self-emission type, and they can achieve a wide viewing angle and high-speed response. Further, the organic EL displays do not require backlights, and therefore they can be made low-profile and lightweight. For these reasons, the organic EL displays attract attention as displays that may replace liquid crystal displays.
An organic EL element, which is the main part of an organic EL display, includes a light-transmitting front electrode, a light-transmitting back electrode facing the front electrode, and an organic layer interposed therebetween and including a light-emitting layer. The organic EL element is a self-emission element of charge-injection type, which emits light as electric current flows through its organic layer.
In order to display an image on an organic EL display, it is necessary to make light emitted by the light-emitting layer output from the front electrode. However, of the light traveling toward the front surface side within the element, light components traveling in wide-angle directions are totally reflected on a surface of the front electrode. For this reason, a great portion of the light emitted by the organic layer cannot be extracted from the organic EL element. In other words, the conventional organic EL display entails a problem of a low outcoupling efficiency.
As a solution to such a problem, Japanese Patent No. 2991183 discloses a technique which utilizes a diffraction grating. With this technique, the outcoupling efficiency of the organic EL element can be raised. However, the present inventors have found through the process of achieving the present invention that the viewing angle is significantly narrowed if a diffraction grating is used to raise the outcoupling efficiency in the organic EL element.